There are hints given on the bottom left: time, day, week, month and year. What do they mean? First, focus on the centered words/phrases for each:
현재 - the present,
오늘 - today (or sometimes, the present),
당일 - the (very) day or today,
이번 주 - this week (= 금주),
이번 달 - this month (= 이달),
and 올해 - this year (= 금년)
Then, think about what should be placed next to them. Then you'll find what I mean. For example, 어제 is placed before 오늘, so 어제 means "yesterday." And 그제 is placed before 어제, so 그제 stands for the day before yesterday. That's the proper way to understand what this video says.